Park brake on your Cargo is designed to stay on when air pressure is low so your problem, may be an air leak causing the pressure to drop too much and too quickly. When parked for any length of time ie overnight you can expect some air loss and should be prepared to wait for full air pressure.
If you are parking for very long time you may get pads sticking to discs, this usually is in weeks, even months.
Lastly there may be problems with your calipers (the bits that actually op brakes) ... this was a common problem on Cargo's but they do not normally free off.
This info is based on you having disc rear brakes rather than drum, although the air issue works the same for both and shoes can stick to drums in lengthy parking up.
Kevin Handley, June 2007
